Fire extinguishing system



May 27, 1947. s. T. VAN HOUTEN FIRE EXTINGUISHING SYSTEM 2 Sheets-Sheet 1 Filed Dec. 11, 1942 'INVENTO. Jig Mm T142111 Hoafgn May 2?, 1947.

s. T. VAN HOUTI'EN FIRE EXTINGUISHING SYSTEM Filed Dec. 11, 1942 2 Sheets-Sheet 2 I E N 0 m M m h m k W 53 J Patented May 27, 1947 UNITED STATES OFFICE FIRE EXTINGUISHING SYSTEM' Stephen T. Van Houten, Allendale-,N J. Application December 11, 1942, seriaiNo: reaper 1 Claim.

This invention relates to that class of fire extinguishing systems known as dry-pipe deluge systems wherein the main riser and the distributing or branch pipes connected therewith are normally free from the extinguishing fluid and wherein the sprinkler heads or outlets are of the open type and at all times in free communication with the piping of the system. Systems-of this character are particularly desirable in unheated properties, such as airplane hangars, in that danger of freezing of the extinguishing fluidin the piping of the system in cold weather to render it inoperative is eliminated, to say nothing of the consequent-damage resulting therefrom by reason of bursting pipes, and the extinguishing fiuid'is immediately discharged in unobstructed streams from the open sprinkler heads upon the opening of the main control valve to thereby enhance the fire controlling: and extinguishing qualities of the system as awhole,

Automatic fireextinguishing systems of theabove character, because of their inherent speed of operation,- have been foundto be peculiarly desirable and successful in the cases'of fires of the flash type thatmight occur in airplane hang ars,- chemical plants, powder plants, plastic manufacturers or in other localities where aflash type of fire hazard exists which might result in a quick-acting, fast-spreading confi'agration. Although the distributing pipes are filled with water or other extinguishing medium in so-called wetpi-pe systems, to insure ready and quick discharge of the medium in the event of a'fire, this advantage is somewhat ofiset in systems of thattype' by reason of the fact that normallyclosed fusible sprinkler heads are usually employed, in contradistinction to systems of the present type, to prevent premature discharge of the extinguishing medium until a fire occurs so that, of necessity, there must be some delay in the discharge ofthe extinguishing medium to the fire until the sprinkler head or heads fuse andopen. Very often this delay in the fusing-and opening of aspi inklerhead, although the-delay maybe relatively short, is sufficient to permit a fire to reach a condition of confiag-ration beyond the-capacity of the system to control and extinguish Or a conflagration of such large and disastrous-v proportions as will result in: serious property damage before the system functions;

While ithas been recognized that a dry-pipe deluge system has many meritorious advantages over others, some opposition thereto has-been made on the part of insurance and underwriting agencies on the ground that they do not give any supervision of the sprinkler piping, that is, the piping is not under supervising pressure, in order that it may be determined whether the system as a whole is at all timesin proper and operative: condition and" readyi'to function. immediately in serviceable and operable.

,2 theevent ef tlieoccurrence-of a-fire. This criticism is not without merit as such systems em ploying open sprinkler heads; at" th'ep'res'ent time given'o' indication-as towhether the apparatus'is In other words, the piping isnot supervised, which is" undesirable especially when pardons thereof are located re rnotefron r the mechanism of' the main installatiorr and such portions have lain dormant for a considerable time and have become 'covere'dwithdust and dirt; casesof this character expo-- rieric'e' hasshown that workmen or others, 0bserving such empty: pipes with" open sprinklerheads,- i in" apparently abandoned and unse'rvi'ceable conditiom-have disconnected them from the system concluding that they are unusable and havebeendiscarded-and:have: utilized such pipes for" other purposes such as to" make emergency repairs etcl-with the thought of the conservation of: materials and" the" saving: or expense and/or theh'asteriingof production; error of this character is readiIy underStandabIe as'th'e' empty and; dusty pipes very: often give every indication of being aideazd and useless: part of a sprinkler system and or no practical value. A further disad-vantage or: a dry-pipe" deluge system employing opemsprinklerzliead's lies the fact that'the open heads obviously collectdust, sediment, chips and otherlforeign matterwliich: may-obstruct the free flow-of the-extinguishing fluid through the pipes and; from. the iheads=.the'reby impeding; if not defeating,; the'successful' operationof the system.

The primary obj'e'ctzofothe invention is to obviate the objections lust: noted in a dry-pipe deluge fire extinguishing system, especially any illadvised possible removalof' an'y of the systempiping, while preserving all the tried and'best'fea tures-an'd advantages" now present in standard types-1oflextinguishing systems havingsupervisedpiping. To aid in? accomplishing the results soughtlafter; whilepermitting'supervision of the pi ing-of: the system; it is proposed to seal the open sprinkler heads against the collection of dust, foreign matter, etc., and therebyprevent corrosionor otherdamage to the piping, theseal:

providing a closure of a character adapted to prevent the escape of: the: supervising air pressure i-n'the piping? but which-shall be rendered inop erative as a seal and permit the flow of th'e'extinguish-ing fluid 'therethroughbythe pressure of A further object of the invention is the inclusion in a system of the above character of one or more thermostats or heat detecting devices responsive to the action of heat and operable either on the rate-of-rise of temperature principle or the fixed temperature principle, or both of them, these principles being now well-known and understood in the art, said devices being adapted to be connected with and to operate instrumentalities permitting equalization of theair pressure in the system with that of the atmosphere and to thereby enable the main control valve to be opened by the pressure of the extinguishing medium.

Other and further objects and advantages of the invention consist in the inclusion in a fire extinguishing system of the above character of manual means for controlling the electric circuit connecting the aforesaid thermostats and instrumentalities whereby the device may be operated manually instead of automatically; means for giving a signal when said circuit fails; manual means for permitting equalization of the air pressure in the system with that of the atmosphere independently of the operation of the thermostats or heat detectors; the inclusion of one or more fusible sprinkler heads should the thermostats fail to operate and in some cases of combined fusible sprinkler heads and relief valves for permitting equalization of the air pressure in the system with the atmosphere before the fusing and opening of the sprinkler head; means actuated by the pressure of the extinguishing fluid for giving a signal upon the opening of the main control valve; automatic means for maintaining the air pressure in the system, at a predetermined amount; means for giving a signal when said automatic air pressure maintaining mean fails; means for giving a signal when, the gate valve for permitting the flow of the extinguishing medium to the system is closed and electrically operated means for iving signals both locally and remotely of the system when it functions.

Other and further objects and advantages of the invention will appear from the accompanying description, the invention consisting in the improved fire extinguishing system and parts thereof hereinafter more particularly described and then specified in the claim.

Referring to the accompanying drawings which shows. practical embodiment of the invention in a preferred form:

Fig. 1 is a side elevation (partially diagrammatic) of a fire extinguishing system embodying the invention of the application.

Fig. 2 is an enlarged elevation (partly in section)1 of certain parts of the system illustrated in Fig.

Fig. 3 is an enlarged section of one of the improved forms of sprinkler heads employed in the system, and

Fig. 4 is an elevation of a part of the system.

. Referring in detail to the several figures of the drawings:

Reference numeral It] indicates a lead-in pipe for supplying a fire extinguishing medium, such as watento the system and it may be connected with a source of supply as from a city water main which supplies water under pressure. Said pipe connects with a suitable riser l I extending upwardly through one or more floors of a building and branch or distributing pipes l2 are connected to said riser H and extend laterally therefrom adjacent the ceiling l3 of the room or other enclosure of each floor. A conventional manually controlled gate valve of any suitable construction and the housing of which is indicated at I3 is employed for controlling the flow of water from pipe 10 through the riser. The operating wheel for opening or closing said gate valve is indicated at M. The shaft l5 of said gate valve which also carries the operating wheel I4 extends through a supporting cylindrical housing l6 and is threaded through the outer wall thereof. Said shaft I5 is grooved as at ll for reception of the end of a rod l8 extending through an opening in the wall of the housing which slidably supports the rod. Said rod I8 is pivotally connected, as shown, to a contact lever H) which in turn is pivoted to an extension 26 connected to said housing. A tension spring 2| is secured to said lever l9 and to a lug or projection 22 connected to the extension 20. Said spring normally urges the end of the rod l8 into engagement with the periphery of the shaft (5 and when it engages within the groove ll thereof, the gate valve is in open position thereby permitting free flow of the extinguishing fluid from its source into the riser.

The system, of course, is inoperative for fire control and extinguishing purposes when the gate valve is closed because of failure of the flow of the extinguishing fluid thereto. Accordingly, I have made provision for th giving of a signal, such as the sounding of an alarm, when the gate valve is closed and in inoperative position either from design or inadvertence. This alarm in the present instance takes the form of a bell 23 connected by conductor 24 to a source of current supply, such as a battery 25, which in turn is connected by conductor 26 to lever L9. The bell 23 is also connected by conductor 21 to a contact 28. When the operating wheel I4 is rotated to close the gate valve the end of the rod 18 rides out of the groove l1 and onto the high portion of the periphery of the shaft I-5 thereby forcing the lever I 9 upwardly, and in an obvious manner, to move its end into engagement with the contact 28 and thereby close the electric circuit and energize the bell or other signal 23. When the operating wheel I4 is again rotated in the proper direction to open the gate valve, the end of the rod l8 thereupon again becomes engaged within the groove I! by the action of spring 2| to break the connection between the end of the lever l9 and the contact 28 and de-energize the signal.

The housing chamber for the automatic main differential control valve is indicated at 29 and it is incorporated or included within the riser Ii. Said main control valve includes a valve clapper 30 pivoted as at 3| and provided on its lower face with a compressible sealing gasket 32 for engagement with a valve seat 33 also having a compressible sealing gasket 34 secured thereto so that a fluid-tight connection is provided between the valve clapper and its seat when the clapper is in closed position. An auxiliary disk clapper is indicated at 35 and is pivotally connected to an arm 36 of clapper 30. Said auxiliary clapper is adapted to tightly engage valve seat 3'! when the main control valve is closed. The closure of the valve results in the formation of an intermediate chamber 38.

It will be understood that the riser and the distributing pipes of the system are normally filled with air under supervision pressure which, in some cases, may be as low as from two to three pounds per square inch and which, although even when low in amount, is suflicient to hold the main control valve in closed posi; tion inasmuch as the upper side of the clapper 30' against which the pressure is exerted is of considerably larger area than the area of the face of. the clapper 35 which is subjected to the relatively greater pressure of the extinguishing fluid flowing from the source of supply. Release of the pressure against clapper 3!), however, permits the pressure of the extinguishing fluid to automatically open the main control valve, as shown in Fig. 2, whereby the extinguishing fluid will flow upwardly through the riser and into the distributing pipes for discharge from the sprinkler heads.

The intermediate chamber 38 is connected by a pipe 39. with a fluid pressure chamber 40 within which a flexible diaphragm (H- is mounted and which is retained in normal and inoperative position by means of a spring 42 interposed between the diaphragm or a supporting portion therefor and the upper wall of the chamber. A rod 43' is connected to the diaphragm or its support and it is pivotally connected to a cross-arm 44 an end of which is pivoted as at 45 to an extension on the pressure chamber casing. The other or free end of said cross-arm 4 3 carries an adjustable contact screw 35 adapted for engagement with a contact til. Cross-arm M is electrically connected by a conductor as. which in turn is connected to a battery so or other source of current supply and thence to a bell or other signal 5t] which is connected by conductor 5i to said contact il. When the main control valve has opened and the apparatus functions, the extinguishing fluid which flows through pipe 39 into chamber ll exert-s pressure upwardly against the diaphragm dl against the action of spring 42 to rock the cross-arm as on pivot 45' and bring contact 46 into engagement with contact 41 and thereby close the circuit and energize the bell or other signal 50. Pipe 39 is provided with an openended pipe comprising a ball check valve 52 the ball valve memberof which is indicated at 53.

' Pressure of the extinguishing fluid forces said ball member into closed position or that position shown in Fig. 2 but when the main control valve is closed the drip valve is open and the ball assumes the position shown in dotted lines in Fig. 2.

An air relief valve chamber is indicated at 54. His provided with a valve seat 55 for reception and closure by a valve head 55 provided with a laterally extending slidable stem 57 passing through and supported by a stuffing box 53 and carrying a trip head 59 on the end thereof. A spring 60 which encircles the stem 51 by its action normally tends to hold the Valve head 56 in retracted and closed position within the seat 55. A pipe 6! connects the relief chamber 54 and the main control valve chamber 29 and a pipe 52 connects said relief chamber and the pipe 39.

It is desirable and important that the air pressure in the riser and distributing pipes be maintained at a constant and predetermined amount. Provision accordingly has been made for automatically accomplishing that purpose. An air pressure chamber is indicated at 63. It may be of any desirable construction and similar, if convenient, to the construction of air. chamber 45 previously described. Said chamberis connected by a pipe 5% with the riser II and suitably mounted therein is a flexible pressure responsive diaphragm 55 connected by a rod 66 to an arm 61 which is pivoted, as at 68, to an extension on said chamber. A spring 69 is interposed between the iaphragm and a wall ofsaid chamberand tends by its action to urge the diaphragm upwardly against the action of the pressure of air in the. system and in the pipe (i l. The arm 51 carries an adjustable contact is adapted for engagement with contact H which is connected by a conductor 12 with a motor 13 for driving an air compressor I l connected by air pipe l5 with pipe 54. Arm 5! and motor 13 are connected by conductors l6. and Tl respectively with a source of current supply (not shown). Conductors Hi and H: are connected to a coil magnet 18 of a relay (9. When the current supply fails for any reason the coil magnet l8 becomes de-energized releasing an armature Bl] which, by the action of a spring 8], is moved into engagement with a contact 82. Contact 82 is connected by conductor 83, with a battery 85 and thence to a bell or other signal 85' which in turn is connected by conductor 85 with said armature 80. Accordingly, when the main; source of current fails, signal or bell 85 is energized as the circuit is closed by engagement of. the armature Bl) with the contact 82.

When the pressure of air in the system falls below a predetermined constant amount the diaphram 53 is forced upwardly by the action of the spring 69. This brings the contact is intoengagement with the contact H to close the circuit and drive th motor 13 which in turn operates the air compressor M until such time as the air pressure in the system has reached the predetermined required amount. The result is that the diaphragm 65 is again deflected or distended downwardly by the pressure of air in pipe 64 andv against the action of the spring 65 and the contact in is thus released from its engagement with the contact H to thereby break the circuit and stop the motor 13 thereby discontinuing the action of the air compressor 14.

Mounted on the ceilings I3 at spaced distances apart are a plurality of electric thermostats or heat detecting devices 8? which are responsive to the action of heat, such as the heat generated by a fire. They are preferably constructed to operate either on the rate-of-rise of temperature. principle or on the fixed temperature principle, or both, and their specific construction may vary considerably although, if so desired, they may be of a construction such as is shown and described in my prior patent for Fire extinguishing and signalling unit, No. 2,267,484, dated December 23, 1941. These electric thermostats are connected by conductors 8.8 and '85 to a standard electric panel box the interior construction of which it is unnecessary to describe in detail but which contains such switches, relays and other instrumentalities as will permit an electric current to be distributed therethrough in such manner that the various devices connected therewith will function properly in the manner described herein. Said panel box derives its electric energy from a source of current supply, as from a battery 9i, and connected to the panel box is a troublebell 92 or other signal connected to a battery (not shown) or other source of current supply whereby the bell 92 will sound an alarm should the main source of current supply in fail. Conductors 93 and 9 3 connect the panel box with a coil magnet 95 mounted in spaced but operative relationship to a pivoted detent 96 providedwith a latch 91 normally engaging and holding a pivoted lever 53 carrying a weight 99 in inoperative position. When the coil magnet 95 is electrically energized by the current flowing through conductors 93 and 94, detent 96 is drawn into engagement with the magnet to release the latch '91 action of the spring 69.

from its engagement with lever 98 permitting it to be rocked in a clockwise direction by the weight 99 which strikes against the head 59 to open the valve 56 and hold it open against the This permits the air under pressure in the system to flow through the pipe Bl, relief chamber 54, pipe 39 and into the intermediate air chamber 38 which, obviously, equalizes the pressure of air on either side of the valve clapper 30 and permits the main control valve to be forcibly swung into open position by the pressure. of the extinguishing fluid against the underside of the clapper 35.

Mounted on and communicating with the distributing pipes H are a plurality of sprinkler heads spaced from each other and the bodies of which are indicated at 1813. They are provided, as ordinarily, with screw-threaded shanks [EH integral therewith adapted to be threaded within suitable correspondingly screw-threaded openings in the distributing pipes. Said bodies are provided with openings or passageways I02 and with circumferential grooves I83 adjacent their upper ends. Extending upwardly from the bodies and preferably integral therewith are the supporting arms or frames I04 terminating at their upper ends in a plurality of deflecting and spreading devices H15 in substantial vertical alignment with the openings I02. The sprinkler heads described normally are of a type permitting the extinguishing medium, such as water, as soon as it flows into the system, to be discharged freely through the openings I02 and upwardly against the deflecting devices I05 which in turndeflect the water downwardly and outwardly in a limited area over the conflagration to be extinguished. According to the present invention, these improved sprinkler heads preferably are provided with frangible seals or closures to retain the supervising air pressure in the system and to obviate certain disadvantages which ordinarily prevail when ordinary open sprinkler heads are employed and. which have been previously catalogged in detail. Accordingly, I propose to cover or close the sprinkler heads described herein with caps or closures which are removable, rupturable or otherwise rendered inoperative as closures by the pressure of the extinguishing fluid but which are inert to the supervising air pressure in the system. For this purpose it is preferred to employ a, cap HEB comprising a rupturable materal, such as .sheet rubber, the peripheral edge of which is locked within the groove 163 by means of a split ring 01' band it! Whose meeting ends are clamped together by any suitable form of clamp or coupling 198. In some cases the cap may comprise a material which is not necessarily of a rupturable character and which is held on the head by friction or cement or otherwise and sufficiently tightly to withstand the force of the air under pressure in the system but insufficiently tightly to withstand the pressure of the extinguishing fluid Which, when exerted against the cap, will remove it bodily or blowit off its seated position on the sprinkler head.

In addition to the employment of the particular sprinkler heads of the character just described, it may sometimes be desirable to employ one or more closed sprinkler heads of the fusible type and as indicated at m9 which are now very well-known in the art and which utilize a fusible link H8 which is fusible by. theaction of heat, as the heat generated by a fire, in order to open the head and permit the discharge of the extinguishing fluid therefrom. While sprinkler heads of this character are now standard and in universal use the chief objection thereto lies in the fact that, of necessity, some delay occurs before the sprinkler system can operate because of thetime necessary for the fusing of the fusible element or link to permit the head to open. In still other cases it is sometimes desirable to employ, in addition to the novel sprinkler heads described, one or more closed fusible sprinkler heads having a relief valve I l I associated therewith and the function of which is to permit the discharge of the air under pressure in the system prior to the fusing and opening of the closed sprinkler head. The relief valve is responsive to a sudden rate-of-rise in temperature as,- for instance, a sudden temperature rise occasioned by a fire which acts to automatically actuate the valve and permit the escape of the compressed air in the system. Any suitable valve which will attain the desired result may be employed, such valves now being old and well understood in the art as exemplified, for instance, by that shown and described in the patent to Grifiith, No. 1,909,490, dated May 16, 1933. Accordingly, a detailed explanation of the interior mechanism and parts of the valve in question will be found unnecessary.

It will be observed from the foregoing description that when the system is filled with air under pressure and the automatic main control valve is closed, it is preferably held in closed position by such air pressure but that when the air pressure is released, said control valve is automatically opened to permit the flow of the extinguishing fluid to the riser and distributing pipes and to open the sprinkler heads I00 by rendering their caps inoperative as closures by the pressure of the extinguishing fluid itself. When one or more of the thermostats or heat detectors 81 are subjected to heat, as from that generated by a fire, the opening of the main control valve is effected automatically in that the circuit between the conductors 88 and 89 is closed and flows through panel box 90, through conductors 93 and 94 thus energizing the coil magnet 95 and actuating the devices associated therewith in the manner previously explained which results in the equalization of the air pressure on each face of the clapper 38. This also results in the sounding of the alarm 50. In order to permit manual, instead of or in addition to automatic, closing of the main circuit, which may be desirable in some cases, I have provided one or more manually operated electric switches H2 of any suitable conventional construction which are connected to the conductors 88 and 89. 'Air pressure in the system of a predetermined constant amount is automatically maintained by means of the air compressor 74 and associated parts which operate in the manner previously described.

It will be further understood that the apparatus will function properly whenever the air pressure in the system is released independently of the automatic operation of the electrically actuated thermostats 87 and the various mechanisms controlled thereby or the manual operation of the switches H2. For instance, the pressure in the system may be equalized with that of the atmosphere either by operation of a relief valve HI, the fusing of a fusible link H0 of one of the closed sprinkler heads H19 or by means of any desired form of manually controlled air valve H3 connected to and communicating with one of the distributing pipes I2 which may be manually operated and opened by manipulation of a pivoted lever or handle I I4. When the system is operated electrically by action of one or more of the thermostats or heat detectors 8'! it is desirable that a local signal be energized. This signal may take the form of a bell H which is connected by conductors I I6 and I I? to the panel box 96 whereby the bell is sounded when the circuit between conductors 83 and 89 is closed.

It will be understood in some cases that the main control valve may be held in closed position by means other than by the air pressure in the system as by a latch or detent, or any other mechanical device or devices automatically releasable electrically or otherwise whenever any of the heat-responsive devices functions under the action of heat, as that occasioned by a fire. Numerous examples of mechanisms for accomplishing this result may be found in the prior art.

It is also desirable that an additional signal or signals be given at a point remote from the installation as, for instance, at a fire house when the apparatus functions. Accordingly, conductors H6 and II! have been connected by conductors I I8 and I I9 respectively to a coil magnet I20 which, when energized, draws one end of a pivoted arm I2I into engagement therewith against the action of a spring I22. This movement of the arm I2I releases a hook I23 on the other end thereof from its engagement with a notch in the peripheral edge of a clock I24. Said clock is adapted, when released from engagement with said hook I23, to send code or other signals to a trouble register I25 usually located in a central station. Said register is connected by a conductor I26 to a pivoted contact I2'I which engages a pivoted contact I28 the free end of which bears against the peripheral toothed edge of the clock I24 whereby the desired interrupted code signals are given when the clock is in operation. Contact I28 is also connected by a conductor I30 to a battery or other source of current supply I3I which in turn is connected to a bell or other signal I32. A conductor I33 also connects the bell with the trouble register I25 for completion of the electrical circuit.

When the main control valve has opened and the bell 50 has been energized because of the pressure of the extinguishing fluid flowing through pipe 39 and against diaphragm 4| to close the circuit in the manner previously described, it is also desirable that signals H5 and I32 and trouble register I25 be energized simultaneously. Accordingly, conductors 48 and 5| are connected by conductors I34 and I 35 respectively with a suitable relay (not shown) within the panel box 90 which in turn is connected with the conductors I I 6 and I I1.

When the main control valve is held in closed position other than by the supervising air pressure in the system and is in no wise dependent thereon, it is desirable that a signal be given when such air pressure has been released as, for instance, by a breakage of one of the distributing pipes or .by any leak of large proportions in the system beyond the capacity of th pump I4 to maintain the pressure at a predetermined fixed amount. Accordingly, an extension pipe I36 is provided (Fig. 4) and communicates with and is connected to the pipe 64 previously described as well as with an air chamber I3'I within which a light flexible diaphragm I38 is mounted. Said diaphragm is held in expanded or distended position by the supervisory air pressure in the system and is connected by a rod I39 to an arm I40 pivoted, as at I4I, to an extension on the air pres- 10 sure chamber casing. The arm I40 carries an adjustable contact screw I4! adapted to engage a contact I42 connected by conductor I43 with a battery I44 which in turn is connected with a bell or other signal I45. Said bell I45 is connected by conductor I 46 with the pivot I4I or the extension supporting it. Release of the air pressure in the system and against the diaphragm I38 permits movement of said diaphragm by the action of a light spring I4'I in an obvious manner, which carries the contact I4I into engagement with the contact I42 to close the electrical circuit and energize the bell I45. The diaphragm and adjacent parts are adequately balanced and adjusted and readily actuated because of the relatively low air pressure in the system.

Various modifications may be resorted to without departing from the spirit of the invention as set forth in the appended claim.

The invention claimed is:

A differential pressure operating dry-pipe fire extinguishing system for discharging an extinguishing fluid under pressure and normall containing a controlling body of air under pressure including, in combination, a sprinkler head having a discharge outlet, a main control valve communicating with a source of extinguishing fluid under pressure and adapted to be normally held in closed position against the pressure of the extinguishing fluid by air confined under a predetermined normal pressure in the system between the valve and sprinkler head, heat responsive means operating on the rate of rise principle for releasing air from the system, and a closure means for the outlet in the sprinkler head operative to normally confine the air against escape through the sprinkler head so as to keep the valve closed under the air pressure against the pressure of the extinguishing fluid, said closure means being inert to heat and to the normal air pressure in the system, but responsive to the pressure of the extinguishing fluid when air is released and its pressure reduced relative to the pressure of the extinguishing fluid to open the outlet in said sprinkler head.

STEPHEN T. VAN HOUTEN.

REFERENCES CITED The following references are of record in the file of this patent:

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